(1) Field of the Invention
This invention relates generally to the control and operation of data printing machines; and, more particularly, to setting and varying the margins and line spacing of printed data and determining the direction of printing.
(2) Prior Art
The prior art teaches various mechanical means whose adjustment or manipulation before printing begins, or during interruption in printing, will institute changes in the margins and spacing between lines of printed data. For example, mechanical limits or stops can control the extremities of travel of a print head and can be adjusted to a desired position before printing begins. Similarly, varying the spacing between lines of printed data is usually accomplished by such means as manual adjustment of a mechanical gearing arrangement or slip clutch which vertically moves a printing surface in relation to a printing head. For example, the printing surface (i.e., paper entrained over a roller) can be moved by freeing the roller from its normal drive mechanism and freely rolling it a desired distance, thereby moving the paper with the roller.
Once mechanical margins have been established for a printing machine, it is known that either the left-hand or right-hand margin of a line of printed data can in effect be moved inwardly by the insertion of blank data either at the beginning or ending of the line. The blank data can be inserted by the operator of the printing machine before the affected line starts to print, or can be included in the data introduced into the printing machine. A frequently used method of introducing data into a printing machine is the use of punched cards. To move a left-hand margin of a line of printed data to the right, the punched card would include blank data representative of the desired amount of movement to the right of the left-hand margin. In either case, operator insertion or data insertion, the insertion of blank data would vary a given margin only for a single line of printed data, and subsequent variation of a margin would require subsequent additional introduction of blank data. Also, variation of the margins can only be inwardly relative to the particular margin (i.e., to the right of a left-hand margin, or to the left of a right-hand margin).